Filters for tobacco smoke comprising cellulose esters and ethers



CELLULOSE ESTERS AND ETHERS Filed March 5, 1954 TOBACCO CIGARETTEWRAPPER GEORGE R TOUEY INVENTOR.

AT YURNEYS' l [Ir llllllvlv United States Patent FILTERS FOR TOBACCOSMOKE COMPRISING CELLULOSE ESTERS AND ETHER'S George P. Touey,Kingsport, Tenm, assignor =to :Eastman Kodak Company, Rochester, N. Y.,a corporation of New Jersey Application March 3, 1954, Serial No,413,949 7 Claims. (Cl. ISL-208) The present invention relates to tobaccosmoke filters suitable for use in cigarettes, pipes, and cigarette andcigar holders. More particularly the invention is concerned with novelfiltering material specifically adapted for more-extensive removal ofnicotine and other alkaline ingredients from the smoke.

The prior art discloses a number of cellulosic tobacco smoke filteringmaterials including paper, cotton fibers, Woven cotton and the like.More recently the use of cellulose esters and the like :has been taught:by Berl in U. S. Patent No. 2,228,383, :by Cobb & Hargrave U. S. Patentapplication Serial No. 324,284 filed December 5, 1952, and by Crawford &Stevens in U. S. applications Serial No. 324,342, filed December 5, 1952and Serial No. 374,168 filed August 14, I953.

I now have discovered that a filter of greatly improved efiiciency,particularly as respects removal of alkaline constituents, e. g.nicotine from the smoke may be obtained by employing a cellulosederivative having a plurality of radicals containing free acid groups,said radicals being chemically attached to the cellulose molecule. it istherefore an object of any invention to provide for the removal, duringsmoking, of all or the major portion of nicotine and other harmfulingredients of tobacco smoke. A second object is provision of a noveltobacco smoke filter capable of removing undesirable constituents fromcigarette smoke both mechanically and chemically. Another object relatesto the preparation of cigarette filters wholly or in part :frommaterials consisting of cellulose acid esters and cellulose acid ethers.Other objects Will be apparent from the accompanying specification andclaims.

My invention may be broadly described as residing in an improved tobaccosmoke filter having a mass of filtering-material providing a pluralityof smoke passages therethrough, said material comprising at least asubstantial amount of a substance which is a derivative of cellulose,said derivative having free acid groups chemically at tached to acellulose residue through the oxygen atoms of the hydroxyl groups oroxygen atoms replacing these) of the cellulose. In accordance with theinvention the cellulose derivative most advantageously is selected fromthe group consisting of those cellulose ethers and cellulose esterswhich have reactive free acid groups chemically attached to thecellulose.

The substances which I have found to be most advantageous mayberepresented generally by the formula:

wherein Cell. represents the residue of a cellulose molemile, from whichn hydroxyl groups have been removed, X is an ester or other residuecontaining at least one free organic or inorganic acid radical, and n isa number preferably amounting to at least lfor each 1 0 anhydroglucoseunits originally present in the cellulose molecule. Thus, stated inanother Way, the novel smoke filters comprise derivatives of cellulosecontaining at least one free reactive acid group per ten anhydroglucoseunits of the cellulose and selected from the group consisting of (1)acid esters of cellulose and polybasic acids, and (2) acid ethers ofcellulose and hydroxy acids.

2 The cellulose acid esters contemplated by the invention include:

1. Dicarboxylic acid-esters having one free-acid group, e. g. celluloseacid phthalate, cellulose acid succiuate, cellulose acid. maleate, andcellulose acid malonate. The compounds of this group may be representedby the 2. Trica'rboxylic acid esters including (a) those having one freeacid group, e. g. cellulose acid citrate and cellulose acid carballylaterepresented by the formula and (b) those having two'freeacid groups, e.g. cellulose acid citrate :and cellulose acid 'carballylate representedby 3. Mineral acid esters, including (a) dibasic acid esters, e. .g.cellulose acid sulfate of the formula and ('11-) estersof tribasicacids, -e. g. cellulose monohydrogen phosphate and cellulose dihydrogenphosphate represented by the formulae 4. Mixed inorganic mineral andorganic carboxylic acid esters, e. g. cellulose acetate phosphate,cellulose acetate sulfate and cellulose acetate phthalate.

5. Mixed esters of monoand polybasic acids, e. g. cellulose acetatephthalate.

The cellulose acid ethers contemplated by the invention include:

(l) carboxyalkyl cellulose others, e. g. carboxymethyl cellulose andcarbo'xyethyl cellulose as represented by the formula .(2) alkylsulfonicacid ethers, e. g. sulfoethyl cellulose,

represented by the formula '|7Z Thefilters of the invention may be madein accordance with any of the methods or any of the forms described inthe prior art wherein a foraminous, pervious or porous mass is formedfrom fibers, powder, flake, sponge or the like. Fibrous filterscontaining the novel filtrants and prepared by the methods described inthe Cobb & Hargrave and Crawford & Stevens pending U. S. patentapplications referred to above have proved most advantageous, especiallywhen the filters are composed of fibers or filaments synthetically spunfrom the novel filtering substances and converted into rod-like massesof substantially longitudinally aligned crimped filaments coextensivewith the masses. The novel substances of the invention also may be usedin admixture with cotton asbestos or the like and may be carried onporous supporting material as coatings thereon. It is contemplated thatthe invention will give improved action by the combination of mechanicalremoval of undesirable ingredients by means of impingement, absorption,adsorption and/or condensation and the like, as taught by the prior art,and also by the chemical combination of the free acid groups withalkaline material existing as impurity in the smoke.

In fibrous form, the acid cellulose derivatives of this invention are,as indicated above, ideally suited for the preparation of filter tipsfor cigarettes. A simple method consists in preparing a small wad of thefibers approximately 11 mm. in length and with a thickness equal to thatof a cigarette. This wad is then inserted in the end of the cigarette byprocedures known to the art. In the case of the soluble cellulose acidesters and ethers this wad can be prepared from spun filaments eitherdirectly or in the form of a sliver or tow. Thus, for example, celluloseacetate phthalate can be spun from an acetone solution, and the fibersconverted to a tow from which the filter wad is prepared.

ln powder or flake form, the acid cellulose derivatives are moresuitable for the preparation of filters for pipes or cigarette holders.For such purposes the filter material is usually held in a suitablecompartment within the pipe stem or cigarette holder.

The number of acid groups on the residue of a cellulose molecule doesnot seem to be highly critical although it seems preferable to have atleast one acid group per three units of anhydroglucose. However,substantial amounts of nicotine can be removed with acid cellulosederivatives containing as low as one acid group for every tenanhydroglucose units originally existing in the cellulose molecule.Where other filtering substances are mixed with the free acid derivativein one filter unit, it may be necessary to employ a derivativecontaining a higher percentage of free acid groups. In any event,

While the preferred concentration of reactive free acid be noted thatthe preparation of dicarboxylic acid esters of cellulose'is discussed inHeusers Cellulose Chemistry (page 289), and the preparation of celluloseacid citrate is disclosed in my copending U. S. patent application S. N.355,416, filed May 15, 1953. Preparation of cellulose phosphates isreported by Iergens et al., Textile Research Journal, 18, 42-44 (1948).Procedures for making cellulose acid esters are also described in U. S.Patent 2,505,561. U. S. Patent 2,093,462 discloses methods for thepreparation of cellulose acetate acid phthalate and cellulose acidsuccinate. The preparation of cellulose acid phosphate is disclosed inmy copending U. S. patent application S. N. 264,677, and the preparationof sulfoethyl cellulose is described in my copending U. S. patentapplication S. N. 253,957, filed October 30, 1951.

Carboxymethyl cellulose may be prepared from alkali cellulose andchloroacetic acid in accordance with a reaction which may be representedas follows:

ClOHzCOOH (NaOH) HCl CelL-O CHQC ONa GelL-O CHzCO OH Coll.ONa

CH2=CHCN Cell.0 Na

(NaOH) Cell.-O CH2CHzCN H01 Cell.0 CHzCHzCOONa Gen-00111011200 onSulfoethylcellulose (cellulose ethane sulfonic acid) is a representativeexample of an alkyl sulfonic acid ether of cellulose. It can be preparedby etherifying cellulose with Z-chloroethane sodium sulfonate.

ClCH CHzSOaNfl Ccll.ONa

(NaOH) HCl ll.OCHgCHzSOsNa CGll.--OCHHCH1SO3H One embodiment of theinvention is illustrated in the accompanying drawing which is apartially cut-away view of a cigarette equipped with a filter comprisinga rod-like mass of crimped, longitudinally aligned fibers spun fromcellulosic material having reactive free acid groups.

The invention is further illustrated in the following examples.

Example 1.-Preparati0n of cellulose acetate acid phthalate filter tips Asample of cellulose acetate acid phthalate containing an average of lphthalyl group 0 ebormooom and two acetyl groups for each anhydroglucoseunit was dissolved in acetone and spun into filaments of about 16denier. The filaments were cut into short fibers of approximately inchin length and packed into cigarette paper tubes obtained by the removalof the tobacco from standard brand cigarettes. The rods thus formed werecut into lengths of /2 inch thus producing filter tips. Ten of thesetips were then sealed to the ends of ten cigarettes of a standard brand.The filter tipped cigarettes were smoked on a smoking machine similar inoperation and design to the one described by I. A. Bradford, W. R.Horton, and H. R. Hanmer, Industrial and Engineering Chem., 28, 836-9,1936; Figure 2. As a control run, ten cigarettes of the same brand werealso smoked on the smoking machine. All cigarettes were smoked to a markrepresenting 70% of the total length of the cigarette and the smoke wascollected in a mixture of chloroform and 5% aqueous sulfuric acid. Afterthe completion of the smoking procedure the chloroform-sulfuric acidmixture of each run was separated. The sulfuric acid layers wereanalyzed for nicotine according to the silicotungstic acid proceduredescribed in Methods of Analysis, Association of Official AgriculturalChemists, 7th ed., pp. 69-70 (1950). The chloroform layers were analyzedfor dissolved solids or tars by evaporating ofi the chloroform anddrying the residues at C. until constant weights were obtained. Theamounts of nicotine and tar found in the smoke from the filtered andunfiltered cigarettes are given in the table below.

mg. Tars mg.

Nicotine 10 cigarettesno filters 158 20 10 cigarettes-filter tips added100 5 Example 2.Preparati0n of cellulose acid succinate filter tips Afibrous cellulose acid succinate was prepared by allowing 10 grams ofcotton linters to react with 50 grams of succinic anhydride in ml. ofpyridine at 65 C.

for 48 hours and precipitating the dope which formed in dilute aqueousHCl. This washed and dried acid ester containing approximately 50%succinyl was cut, packed into cigarette paper tubes, and converted tocigarette filter tips in the manner described in Example 1. These filtertips were then sealed to the ends of ten cigarettes of a standard brandand smoked on the smoking machine (Example 1). As a control tencigarettes of the same brand but without filter tips were also smoked onthe smoking machine. The amounts of nicotine and tar found in the smokefrom the filtered and unfiltered cigarettes are given in the tablebelow.

Example 3.Preparati0n of cellulose acid citrate filter tips A ZO-gramsample of long-fibered cotton was soaked for 20 minutes in a 35% aqueoussolution of citric acid, pressed to a weight corresponding to 1 partcotton and 1 part citric acid, and dried for hours at 105 C. The washedand dried product was a cellulose acid citrate with a free carboxylcontent of 11%. This fibrous material was converted into a cotton cordor sliver and wrapped in cigarette paper to form paper rods of thecellulose acid citrate. Finally, the rods were cut into V2 lengths andused as filter tips for cigarettes in the manner described in Example 1.The smoke collected from ten cigarettes containing the cellulose acidcitrate tips gave a test showing that over 70% of the nicotine had beenremoved by the filter.

Example 4.--Preparati0n of cellulose acid phosphate filter tips AZO-gram sample of cotton linters was immersed in a solution containing15 grams of 85% phosphoric acid, 25 grams of urea, and 35 grams ofwater. The ureaphospl'rate impregnated linters were pressed to a weightcorresponding to 1 part cellulose and three parts solution and heated at150 C. for forty minutes. The heated product was washed free of reagentswith water and finally treated with dilute HCl to convert the cellulosephosphate salt into its corresponding cellulose acid phosphate. Thisproduct, when dry, was a fibrous material similar in appearance tocotton linters. It was packed into cigarette paper in the mannerdescribed in the pre ceding examples and cut into filter tips of lalengths. Analysis of the smoke obtained from ten cigarettes containingthe cellulose acid phosphate filter tips indicated that 90% of thenicotine in the main stream had been removed by the filter.

Example 5 .Preparation of carboxymethylcellulose filter tips Twentygrams of cotton linters was rapidly stirred in 4.00 ml. of isopropylalcohol while 60 grams of 35% NaOH was slowly added. After the additionof the alkali, twenty grams of sodium chloroacetate was added and themixture was rapidly stirred and heated to 60 C.

After a reaction time of 2 hours at 60 C. the linters were removed byfiltration and washed in sufficient dilute aqueous HCl to convert thesodium salt of the carboxymethylcellulose to the free acid. This productwas a white fibrous product similar in appearance to cotton linters. Ithad a carboxyl content of 14.5%

The free acid carboxymethylcellulose was tightly packed into cigarettepaper in the form of rods and the rods were cut into cigarette filtertips of approximately b-inch lengths. These tips were placed on 10standard brand cigarettes and the 10 cigarettes were smoked on thesmoking machine. Analyses of the smoke collected 6 from the l0cigarettes and the smoke collected from 10 cigarettes of the same brandwithout the filter tip indicated that 65% of the nicotine in the mainstream smoke was trapped by the filter.

Example 6.Preparati0n of sulfoethyl cellulose filter tips A sample ofcotton linters was etherified with 2-chloroethane sodium sulfonategiving a cellulose ethane sodium sulfonate with an average degree ofsubstitution of one ethane sulfonate group for every threeanhydroglucose units in the cellulose. This fibrous material wasconverted to the free acid by treatment with dilute HCl and dried. Thisproduct removed over 75% of the nicotine from the main stream smoke of astandard brand cigarette.

The term polybasic acids as used herein is intended to include dibasicacids and any acid having more than one acid radical. As respects theesters and ethers of polybasic acids other than dibasic acids, it shouldbe noted that the invention encompasses, in addition to the compoundscovered by the formulae given herein, also those esters and ethershaving a free-acid containing radical linked to a plurality of cellulosemolecule residues, e. g.

I claim:

1. A tobacco smoke filter comprising a structurally unitary, elongated,rod-like mass of coextensive, crimped fibers of an ester of celluloseand a polybasic acid, the fibers of the mass being in substantialparallelism with the longitudinal axis thereof, said ester having atleast one free, reactive acid group per ten anhydroglucose units of thecellulose.

2. A tobacco smoke filter as defined in claim 1 wherein the ester ofcellulose contains at least one reactive free acid group for every threeanhydroglucose unit in the cellulosic portion of the ester molecule.

3. A tobacco smoke filter as defined in claim 2 wherein the ester is adicarboxylic organic acid ester of cellulose having one reactive freeacid group in the residue of each acid molecule.

4. A tobacco smoke filter as defined in claim 3 wherein the ester iscellulose acid phthalate.

5. A tobacco smoke filter as defined in claim 2 wherein the ester is atricarboxylic acid ester of cellulose.

6. A tobacco smoke filter as defined in claim 5 wherein the two of thethree acid groups of the tricarboxylic acid remain free.

7. A tobacco smoke filter as defined in claim 2 wherein the masscomprises a segment of a crimped continuous filament tow, the filamentsof the mass being substantially longitudinally aligned, and having adenier within the range of 1 to 16.

References Cited in the file of this patent UNITED STATES PATENTS2,228,383 Berl Jan. 14, 1941 2,394,887 Berl Feb. 12, 1946 2,592,553Frankenburg et al Apr. 15, 1952 FOREIGN PATENTS 177,706 Austria Feb. 25,1954 250,360 Switzerland June 1, 1948 665,278 Great Britain Jan. 23,1952 695,046 Great Britain Aug. 5, 1953 OTHER REFERENCES Hofipauir andGuthrie: Ion Exchange Characteristics of Chemically Modified CottonFabrics, pages 617-620 of vol. 20, (September 1950) issue of TextileResearch Journal.

Davidson and Nevelle: Pages T59-T60 of volume 39 (1948) of the Journalof the Textile Institute.

1. A TOBACCO SMOKE FILTER COMPRISING A STRUCTURALLY UNITARY, ELONGATED,ROD-LIKE MASS OF COEXTENSIVE, CRIMPED FIBERS OF AN ESTER OF CELLULOSEAND A POLYBASIC ACID, THE FIBERS OF THE MASS BEING IN SUBSTANTIALPARALLELISM WITH THE LONGITUDINAL AXIS THEREOF, SAID ESTER HAVING ATLEAST ONE FREE, REACTIVE ACID GROUP PER TEN ANHYDRGLUCOSE UNITS OF THECELLULOSE.